cambo3d wrote:so which is correct, whats in parenthesis or the calculated value... seems like these values should be the same.? so one is wrong? why would they use 185 = 1A, if 123 is 1amp?

I believe it depends on which version of the RAMBO board you have 1.0 uses a different range than 1.1.The drivers have thermal cutoff in practice you'll hit that long before you get to the maximum rated current.As far as I can see the Digipot circuit just drops some portion of VDD over an inline resistor, 3.3KOhms for 1.1 and 4.99KOhms for 1.0, as far as I can see there isn't enough info in the datasheet to determine what the actual voltage going into the chip will be, I think you'd have to measure it.But the different resistor values result in different ranges on the two boards.

cambo3d wrote:so which is correct, whats in parenthesis or the calculated value... seems like these values should be the same.? so one is wrong? why would they use 185 = 1A, if 123 is 1amp?

I believe it depends on which version of the RAMBO board you have 1.0 uses a different range than 1.1.The drivers have thermal cutoff in practice you'll hit that long before you get to the maximum rated current.As far as I can see the Digipot circuit just drops some portion of VDD over an inline resistor, 3.3KOhms for 1.1 and 4.99KOhms for 1.0, as far as I can see there isn't enough info in the datasheet to determine what the actual voltage going into the chip will be, I think you'd have to measure it.But the different resistor values result in different ranges on the two boards.

I'm glad you brought this up. I read somewhere about soldering a 10K resistor over the 4.99 (R30) on the older cards. Do you know anyone who has done this and is it something we should do to the older cards?

Eaglezsoar wrote:I'm glad you brought this up. I read somewhere about soldering a 10K resistor over the 4.99 (R30) on the older cards. Do you know anyone who has done this and is it something we should do to the older cards?

It would get you in the same range as the newer cards in that 5K and 10K resistors in parallel are ~3.3K, but unless you have an issue with the exiting range of values I don't see any reason to do it.

I'm trying to limit the torque of my extruder. I've been playing with M907 and M908. Throwing incantations at the wall, trying for 10% of full power, but getting anything other than standard behavior would help me zero in. I haven't had any luck knowing that any of the following are changing anything/

I'm upgrading from an EZStruder to a BondTech extruder. There seems to be a bug in slicer or elsewhere where the first layer nozzle offsets are not consistent. I've read many posts about it, but no definitive answer. I have the same problem, which in my case doesn't really affect my parts quality that much, but will cause the EZStruder to skip steps. I've wedged the EZStruder to put a lot of pinch on the filament, because I don't want a damaged filament, or gummed up hob wheel. I'd rather have it skip than 1)eat filament, 2)gum up the hob gear, 3)push out the bowden tube.

I'm running my printer for my business, and trying to get the most performance out of it, and for me, that's running at the highest print speed possible without the struder skipping steps. This is at the highest nozzle temperature possible without coking up the inside of the nozzle. This means that the first layer is at risk of the bed plate obstructing the nozzle, and the struder pushing out the bowden tube, or eating through the filament.

That's why I want to limit torque on the extruder. A mechanical clutch would be a nice alternative.

When the nozzle becomes temporarily obstructed - for example due to a blob or curl-up in the print - then it's better for the extruder to skip steps than to grind the filament down. That way, when the obstruction is removed, extrusion will continue.

A downside is that the reduced torque will reduce the available acceleration if the motor is has a high rotor inertia and the gearing is high. So if the torque is very much higher than needed, then instead of reducing current a lot it may be better to use a shorter motor (with less rotor inertia) or reduce the gear ratio.